Cryogenic rectification such as, for example, the cryogenic rectification of feed air to produce oxygen, nitrogen and argon, requires the provision of refrigeration for the cryogenic rectification plant. Typically such refrigeration is provided by the turboexpansion of a process stream. Turboexpansion is an energy intensive step and it is quite costly especially when larger amounts of refrigeration are required such as when one or more liquid products are required. In the case of cryogenic air separation, when argon product in addition to nitrogen and oxygen product is desired, turboexpansion of feed air can reduce argon recovery.
Accordingly it is an object of the invention to provide a system for providing refrigeration into a cryogenic rectification plant wherein not all of the requisite refrigeration for operating the plant is generated by turboexpansion of a process stream.